German Patent Publication 43 200 007, Bruck, describes a process for radiating emissions which is mild on the skin, using a light source as a component in a tanning system. The light source does not emit, or hardly emits, portions of long wave UV-A radiation. The light source is used in combination with a filter. The light source itself is a non-doped mercury high-pressure discharge lamp. Due to the absorption of radiation in the filter, a portion of the radiant energy is lost in the form of heat. The radiator-filter combination itself may be subject to high temperatures.
European Patent 0 254 111 B1, Eliasson et al., describes a UV radiator which has a discharge space, in which a fill gas is included. The discharge space is delimited by walls. At least one of the walls forms a dielectric. Two electrodes are used; at least a first electrode is located on the surface of the discharge which is remote from the dielectric; this first electrode is linear in form, e.g. a metal strip. The first electrode, as well as the dielectric, are transparent to radiation generated by a quiet electrical discharge. The second electrode has a UV radiation reflecting layer, preferably an aluminum layer. The fill gas is a noble gas, or a noble gas mixture which, under discharge conditions, generates excimers. The fill gas additionally contains mercury, nitrogen selenides, deuterium, or a mixture of these substances, alone, or in combination with a noble gas. The comparatively short wave radiation of the noble gas helium, neon, argon, xenon is, under formation of excimers, in the region of from 60 to 190 nm. This extremely short wave UV range of the spectrum is not suitable for irradiation of the human body, or for tanning. The disclosure also describes a mixture of the fill of xenon and chlorine, which emits radiation in the region of from between 300 to 320 nm, that is, a range suitable for irradiation of the human body.
European Patent 0 254 111, Eliasson et al, provides a good disclosure of radiation in the formation of excimers, and also defines excimers: an excimer is a molecule which is formed by one excited atom and one atom in base state. Upon dissociation of the excimer molecule into its constituents, the binding energy is emitted in form of UV radiation. "Excimer" is a coined word derived from excited dimer; a "dimer" is a diatomic molecule consisting of identical atoms, and excimers are excited diatomic molecules.
Transfer of electron energy into UV radiation is highly efficient with such excimers. Up to 50% of the electron energy can be changed into UV radiation. The excited complexes have a lifetime of only a few nanoseconds, or even less, e.g. tenths of a nanosecond. The wavelength of the emitted radiation is dependent on the gas which forms the excimers; for example, for helium, it is between 60 and 100 nm; for xenon, between 160 and 190 nm.